1. Field of the Invention
The present invention relates to camera apparatuses, such as video cameras, and image processing systems for applying specified image processing to an image signal obtained by camera apparatuses, and more particularly, to a camera apparatus for outputting a digitized image signal and an image processing system provided with the camera apparatus.
2. Description of the Related Art
Computers have recently handled multimedia information, such as images and sound, as their technology has advanced.
For example, an image signal obtained by taking a picture with a video camera is input to a personal computer (hereinafter called a PC) and the PC manipulates or stores the input image signal as motion-picture data. Alternatively, the PC obtains one image among the motion-picture data as still-picture data, places the image on a document, and prints it together with characters.
Since IEEE 1394 has been specified as a standard format of an image signal to be input to a PC, a video camera employing a method (hereinafter just called a digital method) for outputting a digitized image signal (digital image signal) has been commercially sold or proposed.
Such a PC handles considerably smaller amounts of data, such as that generated in the specifications of 320 (horizontal) by 240 (vertical) pixels, 15 frames per second, and non-interlaced scanning, than NTSC-format data, which is generated in the specifications of 640 (horizontal) by 240 (vertical) pixels, 60 fields per second, and 2:1 interlaced scanning, due to the processing-capacity limit of the central processing unit (CPU).
On the other hand, a digital-method video camera usually outputs NTSC-format data generated in the specifications of 640 by 240 pixels, 60 fields per second, and 2:1 interlaced scanning, or data generated in the specifications of 640 by 480 pixels, 30 frames per second, and non-interlaced scanning.
Since the output data rate of the video camera is fixed to a certain rate as described above and the rate is different from that which can be handled by a PC, when a digital image signal output from the video camera is handled in a PC, it is necessary to convert the data rate of the digital image signal output from the video camera into the specified data rate in a conversion circuit built in the PC or to convert it by software processing by the use of a conversion program stored in advance in the PC.
When a conversion circuit is built in a PC to convert the data rate of a digital image signal, since the conversion circuit is very expensive, the cost of the whole system increases.
On the other hand, when the data rate of a digital image signal is converted by software processing in a PC, if the processing capacity of the CPU is not very large, the number of frames per second and the number of pixels in an image displayed on the screen or stored in the PC decrease.